1. Field of Invention
The invention relates to a light source unit which is used, for example, for a liquid crystal projector device in which a high pressure discharge lamp of the short arc type is used and which has a concave reflector.
2. Description of Related Art
For example, a light source unit is used as a light source of a liquid crystal projector device which comprises the following:                a light source lamp comprised of a discharge lamp such as, for example, an ultrahigh pressure mercury lamp, a metal halide lamp or the like; as well as        a concave reflector which has a light projection opening on its front and projects the light emitted by the light source lamp forward with high efficiency.        
FIG. 6 shows one example of a conventionally used light source unit (JP-A-2003-007101) in cross section. The light source unit 10′ has a concave reflector 20′ with a cylindrical neck 25′. A cylindrical base component 40′ with an inside diameter which is matched to the outside diameter of this cylindrical neck 25′ is attached by means of a cement 55′ or the like to the back end of the cylindrical neck 25′ in this concave reflector 20′. A discharge lamp 30 with bilateral sealed closures has a discharge vessel 31′, opposite ends of which are each provided with a hermetically sealing part 33′A, 33′B. The lamp 30 also comprises an arc tube 32′ in which there is a pair of opposed electrodes. The hermetically sealing part 33A′ is provided with a base 45 which is attached in the base component 40′.
Recently, for a liquid crystal projector device, there has been a desire to make them even smaller. It is also required of a light source unit, which is used as an illumination light source, that it be made smaller in order to reduce the size of the receiving space for it. Specifically, the hermetically sealing part 33A′ is mounted directly in the concave reflector 20′ without a base by a means of a cement 55′ or the like, by which a light source unit with a narrow, reduced reflector neck 25′ arises. FIG. 7 shows one example of it (compare also Japanese Patent Publications JP-A-2003-523606 and JP-A-2003-523607, and U.S. Pat. Nos. 6,505,958 and 6,540,379). In this example, a line 60′ which passes through the hermetically sealing part of the lamp is routed via a neck opening 25K of the concave reflector to the outside surface of the concave reflector and is connected to a contact component 91′ which is located on the outside surface thereof. However, since a contact terminal S is arranged by a part of the concave reflector 20′ provided with an opening 24′, the area of the reflector surface which can actually be used is reduced and the function as light source unit is adversely affected. For example, the amount of reflected light flux is even reduced by 2% by a single contact terminal.
Furthermore, since the connection to the contact component 90′ which is located in the concave reflector 20′ takes place by means of the line 60′B from the outer lead 50′B via the opening 24′, there are the disadvantages that the area to be insulated in the vicinity of the concave reflector 20′ is increased and that the insulating distance which is to be ensured by applying a high voltage during starting is increased.
The reflection surface of the concave reflector is formed as a cold mirror which reflects light in the visible radiation range and transmits light in the UV range and the IR range. In the example, in FIG. 7, the coating of the electric line and the like are omitted. On the back of the concave reflector, however, generally, there is a line coated with silicone resin or the like in order to insulate the outer lead as far as the contact component. In a coated electric line on the back of the concave reflector there is, however, the disadvantage that, as a result of the uninterrupted irradiation of the light transmitted by the reflector in the UV range, for example, within a liquid crystal projector device the coating means and the like are subjected to degradation by UV radiation during use, that the components volatilizing from them adhere to the reflector and to the optical lenses in the vicinity and the like, and that the optical properties are damaged by them.